Method in drum winding of a web and a drum winder

Abstract: The invention concerns a method in drum winding of a web (P), wherein the roll (13) that is being formed is supported on winding drums (11,12), as well as a drum winder (10). At least a part of the area that surrounds the roll (13) that is being formed is subjected to a pressure lower than the pressure that prevails in the gap formed by the roll (13) that is being formed and the winding drums (11,12), whereby a floating effect is produced on the roll (13) that is being formed. The drum winder (10) is preferably placed in a vacuum chamber (30).

Description: The invention concerns a method in drum winding of a web, according to the preamble of claim 1, which is based on WO-A-92 033 66. The invention also concerns a drum winder, according to the preamble of claim 5, which is based on WO-A-92 033 66. In drum winding, it is desirable to lower the nip loads produced by the weight of the growing roll, because otherwise the linear loads that act upon the nips usually become excessively high, which results in roll defects. With respect to the prior art, further reference is made, for example, to the publications DE 1,047,001, DE 1,111,496, DE 3,618,955, and US 3,497,151 . In these solutions that are known from the prior art, it is known to pass a pressure into the gap formed by the roll that is being formed and by the winding drums, whereby a relief effect is applied to the roll that is formed, because of which effect the linear loads in the nips cannot become excessively high. In order that the pressure should be retained in the gap formed by the roll and by the winding drums, it is known from the prior art to seal the gap from above and from below, respectively, by means of various sealing constructions. From the paper DE 1,047,001 , it is known to move the upper roll-end sealing unit in the axial direction. From the paper US 3,346,209 , it is known to regulate the pressure present in the gap formed by the roll and by the winding drums by means of the lower drum by moving the drum in the direction up-down. Even though, by means of the prior-art solutions described above, considerable improvement is achieved, they, however, involve certain drawbacks. Sealing of the gap formed by the roll that is formed and by the winding drums is, as a rule, problematic. The pressure always leaks to some extent, which results in problems of dust formation. Owing to the leakage of the pressure, a very large quantity of air is needed to maintain the pressure, which air spreads into the working environment, for which reason the dust is readily separated from the web that is wound and spreads into the working environment. On the other hand, the prior-art solutions restrict or at least hamper some operations that are necessary in the roll formation. One of these operations is, for example, the roll change, wherein, when the roll that is wound becomes complete, a new roll spool must be fed into the gap between the winding drums, the web that is wound must be cut off, and the end of the cut-off web must be attached to the new roll spool. Thus, during roll change, various actuators are needed, such as web holders, cutting means, devices for the feed of a new roll spool, etc. The object of the present invention is to provide an improvement over the prior-art methods of drum winding and drum winders. It is a more specific object of the invention to provide a drum winder that has the same advantages as so-called pressure winders have but in which the numerous drawbacks involved in the prior-art solutions are avoided. The objectives of the invention are achieved by means of a method that is characterized by the features of the characterizing clause of claim 1. The magnitude of the floating effect or floating force depends on the location of the area of reduced pressure that surrounds the roll that is being formed. In the embodiments as shown in the figures in the drawing, the sum, i.e. the resultant of the forces applied to the roll that is being formed and arising from the different pressures surrounding the roll that is being formed lowers the linear load between the roll that is being formed and the winding drum. The objectives of the invention are further achieved by means of a drum winder which is characterized by the features of the characterizing clause of claim 5. In the drum winder in accordance with the invention, it has been realized to produce a negative pressure in at least a part of the area surrounding the roll, the gap forms by the roll and by the winding drums being at a higher pressure, as a rule at the normal atmospheric pressure. In such a case, a floating effect is applied to the roll that is being formed which is similar to the effect produced when a pressure is applied to the gap. By means of the solution of the present invention, a number of remarkable advantages are achieved over the prior-art solutions. The solution in accordance with the invention permits a constantly optimal control of the winding, because the difference in pressure Δp between the gap and the environment subjected to negative pressure can be adjusted to the desired level continuously. Thus, the solution in accordance with the invention permits an increase in the roll diameter to a larger size without harmful roll defects. The solution in accordance with the invention does not hamper the operation of the roll change means, at least not significantly. By means of the solution of the present invention, the dust problems can be eliminated almost completely. Moreover, the solution of the invention attenuates the noise arising from the winding. The invention will be described in detail with reference to some preferred embodiments of the invention illustrated in the figures in the drawing. Figure 1 shows a preferred embodiment of a drum winder in accordance with the invention as viewed from the end. Figure 2 is a front view of the embodiment as shown in Fig. 1. Figure 3 shows a second preferred embodiment of a drum winder in accordance with the invention as viewed from the end. In Fig. 1, the drum winder is denoted generally with the reference numeral 10. The winding drums are denoted with the reference numerals 11 and 12, the roll that is being formed with the reference numeral 13, and the rider roll with the reference numeral 14. The cylinder of the rider roll 14 is denoted with the reference numeral 15. The web P cutter device in the drum winder 10 is denoted with the reference numeral 16, the spool feed device with the reference numeral 17, and the web P threading device with the reference numeral 18. The full roll 13 is removed by means of a suitable remover device. In the embodiment as shown in Fig. 1, a roll ejector 19 is used. The reference numeral 20 represents the spool lock of the roll spool. The drum winder 10 described above is fully in compliance with the conventional prior art, and it does not constitute any part of the invention. According to the basic realization of the invention, the winding part of the drum winder 10 is, in the embodiment of Fig. 1, placed in a vacuum chamber 30. The winding part of the drum winder is understood as the unit that consists of the winding drums, the ejectors, the spool locks, and of the roll. The drum winder also includes a slitter part and an unwind stand. The idea of the invention can, of course, also be applied so that the slitter part and the unwind stand are placed in a large vacuum chamber. The negative pressure is produced in the vacuum chamber 30 by means of a system of suction pipes 31. The seal units between the vacuum chamber 30 and the winding drums 11 and 12 are denoted with the reference numerals 32 and 33. The vacuum chamber 30 must, of course, also be sealed at the end of the roll 13. In Fig. 2, the end seal unit of the roll is denoted with the reference numeral 34. Separate seal units 32 and 33 are not necessarily needed, but the seal part can be integrated, e.g., in the walls of the vacuum chamber 30. As is seen from Fig. 1, the vacuum pump/blower/exhauster 35 produces a negative pressure in the system of suction pipes 31. The reference numeral 36 represents the filter, and the reference numeral 37 the vacuum regulator. By means of the vacuum regulator 37, the level of the negative pressure in the vacuum chamber 30 can be adjusted to the desired level. In order to produce the negative pressure, a system of suction pipes 31 is not necessarily needed, for the exhauster 35 can also be placed inside the vacuum chamber 30. The embodiment shown in Fig. 3 is in the other respects similar to that shown in Figs. 1 and 2, but in the embodiment of Fig. 3 the web P is passed over the reversing roll 40. It should be noticed that, when the web P is being wound, bags, i.e. air bags, may be formed in the surface layer of the roll 13, especially in the case of web materials that are poorly permeable by air. The bag formations produce roll defects, because the air of normal pressure, i.e. of higher pressure, which is present in the gap formed by the winding drums 11 and 12, is placed below the surface layer of the roll 13 that is being formed and induces detrimental bag formation when it has access through the nip formed by the roll 13 and the winding drum to underneath the inlet layer. In the embodiment of Fig. 3, this phenomenon has been eliminated by means of the reversing roll 40. In the embodiments as shown in Figs. 1 to 3 in the drawing, the web P is shown as being passed between the winding drums 11 and 12. For a person skilled in the art, it is obvious that the web P can also be passed equally well either from above or from the front. The mode of introduction of the web P, of course, affects the location of the reversing roll 40. In the embodiments as shown in Figs. 1 to 3, the whole of the winding part in the drum winder is surrounded by the vacuum chamber 30. This is, of course, not necessary, but it is sufficient that at least a part of the area that surrounds the roll 13 has been subjected to negative pressure. The extent of the floating effect or floating force depends on the location of the area of reduced pressure that surrounds the roll. In the embodiments as shown in Figs. 1 to 3, the sum, i.e. the resultant of the forces applied to the roll 13 that is being formed and arising from the different pressures surrounding the roll 13 that is being formed lowers the linear load between the roll 13 that is being formed and the winding drum. In the embodiments as shown in Figs. 1 to 3, the magnitude of the floating force F k depends on the areas of effect and on the levels of the pressures in accordance with the following formula: F k = A 1 p 1 - A 2 p 2 , wherein A 1 is the area of effect with lower pressure p 1 is the level of the pressure A 2 is the area of effect with higher pressure p 2 is the level of the pressure. It is not necessary to use an end-seal unit 34 unless a chamber 30 is used that surrounds the whole roll 13, in which case the space between the roll 13 and the chamber 30 must be sealed by means of some seal unit at the cylinder face of the roll 13. Above, just some preferred embodiments of the invention have been described, and it is obvious for a person skilled in the art that a number of modifications can be made to said embodiments within the scope of the inventive idea defined in the accompanying patent claims.

Claims: Method in drum winding of a web (P), wherein the roll (13) that is being formed is supported on winding drums (11,12), and wherein at least a part of the area that surrounds the roll (13) that is being formed is subjected to a pressure lower than the pressure that prevails in the gap formed by the roll (13) that is being formed and the winding drums (11,12), whereby a floating effect is produced on the roll (13) that is being formed, characterized in that said lower pressure is a negative pressure. Method as claimed in claim 1, characterized in that the magnitude of the floating effect is influenced by means of the location of the area of the negative pressure that surrounds the roll (13) that is being formed. Method as claimed in any of the claims 1 or 2, characterized in that the level of the negative pressure is regulated. Method as claimed in any of the claims 1 to 3, characterized in that, when the web (P) is wound, the web (P) is passed over a reversing roll (40). Drum winder (10), comprising winding drums (11,12) that support the roll (13) that is being formed and a rider roll (14) that presses the roll (13) that is being formed, wherein at least a part of the area that surrounds the roll that is being formed is subjected to a pressure lower than the pressure prevailing in the gap formed by the roll (13) that is being formed and by the winding drums (11,12), characterized in that said lower pressure is a negative pressure. Drum winder as claimed in claim 5, characterized in that at least a unit consisting of the winding drums (11,12), the roll ejectors (19), the roll spool locks (20) and the roll (13) is placed in a vacuum chamber (30). Drum winder as claimed in claim 6, characterized in that the vacuum chamber (30) communicates with a system of suction pipes (31). Drum winder as claimed in claim 6 or 7, characterized in that the vacuum chamber (30) is provided with seal units (32,33) so as to seal the spaces between the vacuum chamber (30) and the winding drums (11,12) and with an end seal unit (34) so as to seal the vacuum chamber (30) at the end of the roll (13). Drum winder as claimed in any of the claims 5 to 8, characterized in that a regulator (37) is fitted to regulate the level of the the negative pressure. Drum winder as claimed in any of the claims 5 to 9, characterized in that the drum winder is provided with a reversing roll (40) so as to pass the web (P) over the reversing roll (40) when the web (P) is being wound.

Inventors: RAUDASKOSKI VESA, RAUDASKOSKI, VESA
Applicants: VALMET CORP, VALMET CORPORATION
Application year: 1994
Main classification: B65H18
IPC codes: B65H18